CN108817675B - Femtosecond laser shock peening enhancement method based on electronic dynamic regulation - Google Patents
Femtosecond laser shock peening enhancement method based on electronic dynamic regulation Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
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- B23K26/352—Working by laser beam, e.g. welding, cutting or boring for surface treatment
- B23K26/356—Working by laser beam, e.g. welding, cutting or boring for surface treatment by shock processing
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Abstract
The invention relates to a femtosecond laser shock strengthening and enhancing method based on electronic dynamic regulation, in particular to a method for regulating and controlling plasma and shock waves by using femtosecond laser double pulses so as to improve the surface quality and performance of a material in a laser irradiation area, and belongs to the technical field of femtosecond laser application. Compared with the traditional laser shock strengthening, the method has the advantages that the femtosecond laser double-pulse technology is adopted to regulate and control the local instantaneous electronic state of the irradiated material, further the eruption state of plasma and shock waves is regulated and controlled, the absorption efficiency of the absorption layer on laser energy is improved, the thermal damage of the material is effectively avoided, meanwhile, the surface quality and the performance of the material in a laser irradiation area are improved to a great extent, further the laser shock strengthening effect is enhanced, the method is suitable for improving the high efficiency of the surface quality and the performance of the material, and the controllable strengthening of the hyperfine and the complex three-dimensional structure can be realized.
Description
Technical Field
The invention relates to a femtosecond laser shock strengthening and enhancing method based on electronic dynamic regulation, in particular to a method for regulating and controlling plasma and shock waves by using femtosecond laser double pulses so as to improve the surface quality and performance of a material in a laser irradiation area, and belongs to the technical field of femtosecond laser application.
Background
The laser shock peening technology is a material surface treatment technology widely applied at present, mainly aims at metal and alloy materials and the like, and has great application in the field of aerospace. The main principle is that high-power-density and short-pulse laser is utilized to induce high-pressure shock waves on the surface of a material, so that the surface layer of the material is subjected to residual stress layer deepening, grain refinement, plastic deformation and the like, and further the anti-fatigue, wear-resistant, corrosion-resistant and other performances of the material are remarkably improved. The peak power of the laser used for impact strengthening needs to reach GW magnitude to form effective impact.
The femtosecond laser is widely applied to the field of micro-nano processing of materials due to the ultrahigh peak power, ultrashort pulse duration and processing precision exceeding the optical diffraction limit. In the laser shock peening process, the current common method is to use nanosecond laser single pulse to carry out shock peening. This method has the following disadvantages: the peak power density of nanosecond laser pulse is limited, the pressure of plasma shock wave induced by the nanosecond laser pulse is weak, and the nanosecond laser pulse has an effective effect of improving the surface quality; in order to achieve a better impact effect, the thickness of the absorption layer is limited when nanosecond laser is used for impact reinforcement, the absorption layer is too thick and cannot impact effectively, but the absorption layer is too thin, so that the surface of the material is damaged; meanwhile, nanosecond laser is accompanied with a heat effect when irradiating materials, so that the materials are possibly melted and a recast layer or a microcrack is generated, and the improvement of the surface quality of the materials is not facilitated; the nanosecond laser has low processing precision, and cannot realize precise impact strengthening on a specific area of the material.
Disclosure of Invention
The invention aims to provide a femtosecond laser shock strengthening and enhancing method based on electronic dynamic regulation and control.
The purpose of the invention is realized by the following technology:
a femtosecond laser shock peening enhancement method based on electronic dynamic regulation and control comprises the following specific steps:
step one, dividing the femtosecond laser beam into two beams by using a partial amplitude method through a Michelson interferometer, respectively reflecting the two beams by a plane mirror and then combining the beams again, thereby modulating the traditional femtosecond laser single-pulse beam into the femtosecond laser double-pulse beam. By adjusting the length of the reflecting arm of the Michelson interferometer, the delay time between two sub-pulses can be adjusted to be 100fs-100 ps.
Covering an absorption layer on the surface of the metal or alloy material to be reinforced, wherein the absorption layer is generally an aluminum foil or a polymer black adhesive tape, and the thickness of the absorption layer is about 50-200 mu m.
Step three, focusing the femtosecond laser double pulses generated in the step one on an absorption layer on the surface of the metal or alloy material in the step two, enabling the absorption layer material to be quickly ionized into plasma in a short time, and rapidly expanding to form shock waves, wherein the shock waves can only be transmitted towards the material direction under the action of a constraint layer, and the metal or alloy material yields under the strong impact of the shock waves. The constraining layer is typically water, air or K9 glass.
And step four, removing the absorption layer on the surface of the metal or alloy material, and in the femtosecond laser double-pulse scanning area, the surface of the metal or alloy material is subjected to huge pressure of shock waves to generate residual stress, dislocation, twin crystals and the like, so that the surface quality and the performance of the metal or alloy material are improved.
The device for realizing the method comprises the following steps: the device comprises a femtosecond laser, a mechanical switch, a first diaphragm, a first continuous attenuation sheet, a beam splitter, a second diaphragm, a second continuous attenuation sheet, a first reflector, a one-dimensional translation stage, a third diaphragm, a third continuous attenuation sheet, a second reflector, a focusing objective, a sample to be strengthened, a three-dimensional moving translation stage and a computer.
Connection relation: the femtosecond laser generates traditional femtosecond laser pulse, the traditional femtosecond laser pulse is divided into two beams of sub-pulse light by the beam splitter after sequentially passing through the mechanical switch, the first diaphragm and the first continuous attenuation sheet, and the first beam of sub-pulse light I is reflected by the first reflector carried on the one-dimensional translation table after passing through the second diaphragm and the second continuous attenuation sheet; the second beam of sub-pulse light II passes through a third diaphragm and a third continuous attenuation sheet and is reflected by a second reflector; the two beams of pulse light are combined together at the beam splitter and focused on a sample to be strengthened through the focusing objective lens, and the sample to be strengthened is fixed on the three-dimensional moving platform. The femtosecond laser, the mechanical switch, the one-dimensional translation platform and the three-dimensional moving platform are all controlled by a computer.
Advantageous effects
1. When femtosecond laser double pulses are adopted for laser shock strengthening, the achievable peak power density and shock wave intensity are improved by several orders of magnitude compared with the conventional nanosecond laser, and the shock strengthening of hard materials which cannot be strengthened by other methods can be realized.
2. When femtosecond laser double pulses are adopted for laser shock strengthening, the absorption efficiency of the absorption layer to laser energy is obviously improved compared with that of the traditional single pulse laser under the same energy density; under the same thickness of the absorbing layer, the method can realize impact strengthening of multiple cycles compared with other methods. The method can effectively reduce the thickness of the absorbing layer and realize impact reinforcement.
3. The femtosecond laser double pulses are adopted for laser shock strengthening, so that the heat damage of recasting and the like which can occur in other methods on the surface of a metal or alloy material can be effectively avoided.
4. The femtosecond laser double pulses are adopted for impact strengthening, and the strengthening efficiency can be regulated and controlled by regulating the energy proportion and the delay time of the two sub pulses; the enhancement is maximized when the energy of the two sub-pulses is the same and the sub-pulse interval is 50 ps.
5. The femtosecond laser double-pulse is adopted for impact strengthening, and compared with the traditional nanosecond laser, the method can realize precise control of a strengthened area and improve the processing precision of the strengthened area.
Drawings
FIG. 1 is a femtosecond laser double-pulse shock-enhanced optical path diagram:
wherein, 1 is a femtosecond laser; 2 is a mechanical switch; 3 is a first diaphragm; 4 is a first continuous attenuation sheet; 5 is a beam splitter; 6 is a second diaphragm; 7 is a second continuous attenuation sheet; 8 is a first reflector; 9 is a one-dimensional translation table; 10 is a third diaphragm; 11 is a third continuous attenuation sheet; 12 is a second reflector; 13 is a focusing objective lens; 14 is a sample to be strengthened; 15 is a three-dimensional moving translation table; and 16 is a computer.
Detailed Description
The invention will be further described with reference to the following drawings and examples:
the parameters of the femtosecond laser used in the experimental process are as follows: the central wavelength is 800nm, the pulse width is 50fs, and the repetition frequency is 1 kHz; in the experiment, a sample to be strengthened selects metal copper Cu with the thickness of about 2mm, and an aluminum foil is adhered to the surface of the sample to be strengthened to be used as an absorption layer, wherein the thickness of the aluminum foil is about 150 mu m.
Example 1:
firstly, using the traditional femtosecond laser single pulse to perform impact strengthening, and measuring the depth of a pit on the surface after impact to be used as a comparison with the surface strength after femtosecond laser double pulse impact strengthening. The schematic diagram of the shock-strengthening light path is shown in the attached figure 1, and the specific processing steps are as follows:
(1) opening the mechanical switch 2 and the second diaphragm 6, closing the third diaphragm 10, wherein only the sub-pulse light I is used for impact reinforcement at the moment, calibrating a light path, and ensuring that laser is vertically incident to the surface of a sample to be reinforced;
(2) the energy of the sub-pulse light I is adjusted to be 30 muJ by adjusting the first continuous attenuation sheet 4 and the second continuous attenuation sheet 7; the energy of the sub-pulse light I is transmitted by a beam splitter 5 by half, the laser energy actually acting on the sample is 15 mu J, the diameter of a focused light spot is about 5 mu m, and the energy density is about 153J/cm2；
(3) The computer 16 controls the three-dimensional moving translation stage 15 to move relative to the laser focus at the speed of 2500 mu m/s, so that the laser scanning area of the sample 14 to be strengthened is subjected to impact strengthening;
(4) the residual aluminum foil on the surface of the sample 14 to be strengthened is removed, and the residue is cleaned by acetone and alcohol, and the depth of the pits on the surface of the sample 14 to be strengthened in the laser shock strengthening area is measured to be about 30 μm.
Example 2:
next, the effect of enhancing the impact strengthening by the femtosecond laser double pulse will be described by taking the femtosecond laser double pulse as an example.
The invention provides a method for enhancing laser shock peening by femtosecond laser double pulses, a schematic light path diagram is shown as an attached figure 1, and the specific processing steps are as follows:
(1) respectively opening the mechanical switch 2, the second diaphragm 6 and the third diaphragm 10, and calibrating a light path to enable laser to vertically enter the surface of the sample to be strengthened;
(2) the energy of the sub-pulse light I and the energy of the sub-pulse light II are respectively adjusted to be 15 muJ by adjusting the first continuous attenuation sheet 4, the second continuous attenuation sheet 7 and the third continuous attenuation sheet 11; since the beam splitter 5 reflects and transmits the reflected light again, the total energy actually applied to the sample is 15 μ J, the diameter of the light spot is about 5 μm, and the total energy density is the same as that in example 1 above;
(3) the computer 16 controls the one-dimensional translation stage 9 to move, so that the optical path difference of the two sub-pulse lights at the beam splitter 5 is 15000 mu m, namely the time delay of the two sub-pulses at the beam splitter 5 is 50 ps;
(4) the computer 16 controls the three-dimensional moving translation stage 15 to move relative to the focus at the speed of 2500 mu m/s, so that the laser scanning area of the sample 14 to be strengthened is subjected to impact strengthening;
(5) the residual aluminum foil on the surface of the sample 14 to be strengthened is removed, and the residue is cleaned by acetone and alcohol, and the depth of the pits on the surface of the sample 14 to be strengthened in the laser shock strengthening area is measured to be about 37 mu m.
(6) And (4) according to the operation of the step (3), adjusting the time delay of the sub-pulse light I and the sub-pulse light II to be 25ps, repeating the steps (4) and (5), and calculating that the depth of the pits on the surface of the sample 14 to be strengthened in the laser shock strengthening area to be strengthened is about 35 mu m after measurement.
(7) And (4) according to the operation of the step (3), adjusting the time delay of the sub-pulse light I and the sub-pulse light II to be 10ps, repeating the steps (4) and (5), and calculating that the depth of the pits on the surface of the sample 14 to be strengthened in the laser shock strengthening area is about 33 μm after measurement.
As can be seen from examples 1 and 2, under the conditions of the same laser irradiation energy density and the same laser scanning speed, the femtosecond laser double-pulse impact strengthening efficiency can be improved by about 10 to 25% compared with the conventional femtosecond laser single-pulse impact strengthening effect.
As can be seen from the experimental results of the double pulses with different time delays in the embodiment 2, the strengthening efficiency can be adjusted and controlled by adjusting the time delays of the two sub-pulses under the same energy density; and when the time delay of the two sub-pulses of the double pulse is 50ps, the impact strengthening effect is maximized.
Claims (5)
1. A femtosecond laser shock peening enhancement method based on electronic dynamic regulation and control is characterized in that: the method comprises the following specific steps:
firstly, dividing a femtosecond laser beam into two beams by using a partial amplitude method through a Michelson interferometer, and recombining the beams after the beams are respectively reflected by a plane mirror, so that the traditional femtosecond laser single-pulse beam is modulated into a femtosecond laser double-pulse beam; the delay time between two sub-pulses can be adjusted by adjusting the length of the reflection arm of the Michelson interferometer;
covering an absorption layer on the surface of the metal to be strengthened;
step three, focusing the femtosecond laser double pulses generated in the step one on an absorption layer on the surface of the metal in the step two, enabling the absorption layer material to be quickly ionized into plasma in a short time, and rapidly expanding to form shock waves, wherein the shock waves can only be transmitted towards the material direction under the action of a constraint layer, and the metal yields under the strong impact of the shock waves; thereby improving the quality and performance of the metal surface.
2. The femtosecond laser shock peening method based on electronic dynamic regulation and control as claimed in claim 1, wherein: step one, the delay time range is 100fs-100 ps.
3. The femtosecond laser shock peening method based on electronic dynamic regulation and control as claimed in claim 1, wherein: in the second step, the absorbing layer is generally aluminum foil or polymer black tape, and the thickness is about 50-200 μm.
4. The femtosecond laser shock peening method based on electronic dynamic regulation and control as claimed in claim 1, wherein: step three the constraint layer is generally water, air or K9 glass.
5. An apparatus for implementing the method of claim 1, wherein: the method comprises the following steps: the device comprises a femtosecond laser, a mechanical switch, a first diaphragm, a first continuous attenuation sheet, a beam splitter, a second diaphragm, a second continuous attenuation sheet, a first reflector, a one-dimensional translation stage, a third diaphragm, a third continuous attenuation sheet, a second reflector, a focusing objective lens, a sample to be strengthened, a three-dimensional moving translation stage and a computer;
the femtosecond laser generates traditional femtosecond laser pulse, the traditional femtosecond laser pulse sequentially passes through a mechanical switch, a first diaphragm and a first continuous attenuation sheet and is divided into two beams of sub-pulse light by a beam splitter, and the first beam of sub-pulse light I passes through a second diaphragm and a second continuous attenuation sheet and is reflected by a first reflector carried on a one-dimensional translation table; the second beam of sub-pulse light II passes through a third diaphragm and a third continuous attenuation sheet and is reflected by a second reflector; the two beams of pulse light are combined together at the beam splitter and focused on a sample to be intensified through a focusing objective lens, and the sample to be intensified is fixed on a three-dimensional moving platform; the femtosecond laser, the mechanical switch, the one-dimensional translation platform and the three-dimensional moving platform are all controlled by a computer.
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| CN109920659B (en) * | 2019-03-19 | 2020-12-01 | 北京理工大学 | Method for high-precision machining of micro super capacitor based on electronic dynamic regulation and control |
| CN109848565A (en) * | 2019-04-02 | 2019-06-07 | 西安交通大学 | Femtosecond laser nanoprocessing method and system based on plasmon nanostructure auxiliary |
| CN110205477B (en) * | 2019-07-02 | 2021-03-30 | 哈尔滨工业大学 | Laser shock peening method for improving laser induced shock wave intensity by adopting time sequence double laser pulses |
| CN112382735B (en) * | 2020-11-17 | 2021-11-12 | 东莞赣锋电子有限公司 | Method for preparing lithium ion battery pole piece by laser cleaning |
| CN113182693B (en) * | 2021-04-29 | 2023-02-07 | 北京工业大学 | Femtosecond laser preparation SiO 2 Method for swelling micro-nano structure on metal interface |
| CN114317938B (en) * | 2021-12-17 | 2023-03-28 | 华东理工大学 | Method for changing mechanical property of thin-wall metal |
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| US6203633B1 (en) * | 1998-08-14 | 2001-03-20 | Lsp Technologies, Inc. | Laser peening at elevated temperatures |
| US6852946B2 (en) * | 2002-12-20 | 2005-02-08 | Caterpillar Inc | Laser-induced plasma micromachining |
| CN101474723A (en) * | 2009-01-21 | 2009-07-08 | 西安天瑞达光电技术发展有限公司 | Optical isolation laser shock processing double-side simultaneous shock device |
| CN102199690A (en) * | 2011-04-21 | 2011-09-28 | 中国人民解放军空军工程大学 | Laser plasma shock wave surface nanocrystallization method for polycrystal metal material |
| CN102489877B (en) * | 2011-12-23 | 2014-09-03 | 河南科技大学 | Laser shock method and laser shock device |
| CN102747214B (en) * | 2012-06-29 | 2014-09-24 | 中国科学院力学研究所 | Multi optical path combined shock peening system |
| CN103343204A (en) * | 2013-07-19 | 2013-10-09 | 江苏大学 | Variable pulse width laser device |
| CN103614541B (en) * | 2013-10-31 | 2015-08-19 | 中国科学院宁波材料技术与工程研究所 | For laser impact intensified device and the laser impact intensified treatment process of workpiece surface |
| CN106905966B (en) * | 2017-01-12 | 2019-08-13 | 北京理工大学 | A method of single layer molybdenum disulfide quantum dot is prepared based on dynamic control |
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